- Title
- Behaviour of quiet time ionospheric disturbances at African equatorial and midlatitude regions
- Creator
- Orford, Nicola Diane
- Subject
- Ionospheric storms
- Subject
- Ionospheric storms -- Africa
- Subject
- Ionosphere
- Subject
- Plasmasphere
- Subject
- Q-disturbances
- Subject
- Total electron content (TEC)
- Date Issued
- 2018
- Date
- 2018
- Type
- text
- Type
- Thesis
- Type
- Doctoral
- Type
- PhD
- Identifier
- http://hdl.handle.net/10962/62672
- Identifier
- vital:28228
- Description
- Extreme ionospheric and geomagnetic disturbances affect technology adversely. Prestorm enhancements, considered a potential predictor of geomagnetic storms, occur during quiet conditions prior to geomagnetic disturbances. The ionosphere experiences general disturbances during quiet geomagnetic conditions and these Q- disturbances remain unexplored over Africa. This study used TEC data to characterize the morphology of Q-disturbances over Africa, exploring variations with solar cycle, season, time of occurrence and latitude. Observations from 10 African GPS stations in the equatorial and midlatitude regions show that Q-disturbances in the equatorial region are predominantly driven by E x B variations, while multiple mechanisms affect the midlatitude region. Q- disturbances occur more frequently during nighttime than during daytime and no seasonal trend is observed. Midlatitude Q-disturbance mechanisms are explored in depth, considering substorm activity, the plasmaspheric contribution to GPS TEC and plasma transfer between conjugate points. Substorm activity is not a dominant mechanism, although Q-disturbances occurring under elevated substorm conditions tend to have longer duration and larger amplitude than general Q-disturbances. Many observed Q-disturbances become non-significant once the plasmaspheric contribution to the TEC measurements is removed, indicating that these disturbances occur within the plasmasphere, and not the ionosphere. Transfer of plasma between conjugate points does not seem to be a mechanism driving Q-disturbances, as the corresponding nighttime behaviour expected between depletions in the summer hemisphere and enhancements in the winter hemisphere is not observed. Pre-storm enhancements occur infrequently, rendering them a poor predictor of geomagnetic disturbances. Pre-storm enhancement morphology does not differ significantly from general quiet time enhancement morphology, suggesting pre-storms are not a special case of Q-disturbances.
- Format
- 104 pages
- Format
- Publisher
- Rhodes University
- Publisher
- Faculty of Science, Physics and Electronics
- Language
- English
- Rights
- Orford, Nicola Diane
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